Seat back with adjustable support

ABSTRACT

A seat back suitable for a vehicle incorporates a mechanically adjustable lumbar support. A flexible panel (9) is mounted by hooks (8) on a rigid frame (6). In the lumbar region pockets (13) formed at the margins of the panel house the central regions (15) of strip spring steel springs (16). The upper and lower ends of each spring curve rearwardly from the panel. The upper ends are interconnected by a cross member (18) and the lower ends are interconnected by a cross member (19). A Bowden cable (22) controlled by a manual or powered actuator is provided for moving the cross members (18, 19) towards each other and thereby causing the central regions (15) of the strip springs to bow outwardly and increase the amount of lumbar support provided by the panel region therebetween.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a seat back with an adjustable support and inthe preferred embodiment provides a seat back suitable for use in avehicle seat in which the adjustable support is in the lumbar region.

2. The Prior Art

Within the automotive industry considerable effort has been expended inrecent years in the improvement of the comfort of vehicle seats.Particular attention has been paid to providing support for the lowerback (usually referred to as the "lumbar region") of the user. With aview to accommodating the requirements of a wide range of potentialusers of the vehicle seat, it has proved to be desirable to provide foradjustable lumbar support.

Adjustable lumbar supports presently available either involve the use ofa selectively inflatable bladder incorporated within the seat back, orinvolve the use of some mechanical adjustment which is effective tothrust the seat back forward (i.e. towards the user) when firmer lumbarsupport is required. Although the systems utilizing inflatable bladdershave been found to be very satisfactory, they are relatively expensiveto provide and their use tends to be limited to relatively expensivevehicles. Existing mechanically adjustable lumbar supports which wouldbe acceptable on a cost basis for less expensive vehicles are, however,less than satisfactory. In particular, in such designs some form ofrigid bar or plate spans the width of the back support in the lumbarregion. Increasing the degree of lumbar support thrusts this bar orplate forward, and whilst this does increase the pressure applied to theback of the user of the seat, the presence of an essentially rigid baror plate has been found to be uncomfortable by users of the seat whenthe system is adjusted to provide a substantial degree of lumbarsupport.

The present invention provides a mechanically adjustable lumbar supportwhich can be manufactured economically and which does not involve theuse of any rigid bar or plate which is thrust forward to increase thedegree of lumbar support provided by the seat.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided aseat back including a rigid frame between the opposite sides of which issupported a flexible panel, the marginal regions of the panel adjacentthe sides of the frame being provided with pockets in which are locatedthe central regions of respective wire or strip springs, the end regionsof each spring extending outwardly from its respective pocket andrearwardly of the seat in a curve; an upper cross member locatedrearwardly of the panel and interconnecting the upper curved regions ofeach spring; a lower cross member located rearwardly of the panel andinterconnecting the lower curved regions of the springs; and means forforcing the cross members towards each other whereby the central regionsof the springs are urged to bow towards the user of the seat and therebyincrease the force which the panel located between the central regionsof the springs applies to the back of the user.

In use of the invention, reducing the spacing between the cross memberscauses the springs to bow in the forward direction of the seat andincrease the force which the panel applies (indirectly) to the back ofthe user. However, no bar or plate is utilized to force the paddingmaterial of the seat cover forwardly and accordingly there is no "hard"bar or plate which the user of the seat can feel.

The panel may be of any suitable material, for example of a rubber, orfabric, or of a rubber/fabric composite. In the particularly preferredembodiment of the invention the material is a rubber/fabric composite asdescribed in our patent GB-A-1500725. This material has provedparticularly comfortable in use.

In a preferred embodiment of the invention a single panel of materialspans the full height of the seat back. The lower portion of the panelis provided with springs, etc., in accordance with the invention, whilstthe upper portion of the panel is supported in conventional manner onthe frame by suitable hooks. In this manner, the required adjustment isprovided in the lumbar region, whilst the panel itself provides a smoothtransition from the lumbar region to the upper back region whereconstant support is required.

In a particularly preferred embodiment of the invention the means forvarying the spacing between the cross members comprises a Bowden cable,the sheath of which is connected to one cross member and the core ofwhich is connected to the other cross member. Suitable means areprovided for drawing the core through the outer sheath in order toreduce the spacing between the cross members. This means canconveniently comprise a manually rotatable adjuster provided on the sideof the seat back.

When the force pulling the cross members towards each other is released,the inherent resilience of the springs will automatically return theseat back into a configuration providing a preset minimum degree oflumbar support.

The above and other features and advantages of the Invention will becomeclear from the following description of a preferred embodiment thereof,given by way of example only, reference being had to the accompanyingdrawings:

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 illustrates schematically from the rear a seat back according tothe present invention; and

FIG. 2 is a schematic view on the line II--II of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings, there is shown a seat back 1 suitable forincorporation into the seat of a motor vehicle. It will be appreciatedthat the seat back 1 will, in use, be associated with a seat platformand the back and platform will be covered with appropriate padding andupholstery material as is conventional within the art.

The seat back 1 comprises pressed steel side members 2,3 interconnectedby a top member 4 and a bottom member 5 to provide a rigid frame 6. Theexact form of the frame is not critical to the present invention andthose skilled in the art will be familiar with the general constructionof such frames. For the present purposes, all that need be stated isthat the frame 6 is rigid and is furnished with a plurality of apertures7 for receiving hooks 8. The hooks 8 support within the frame a panel 9of flexible material. In the illustrated embodiment of the invention thepanel 9 is of material substantially as described in our British patentGB-A-1500725 and comprises a central zone 10 of a woven fabric material,marginal zones 11 of a woven fabric material and intermediate zones 12of rubber secured to the fabric zone in order to allow for resilientdeformation of the entire panel.

The fabric material 11 in the marginal zones defines at each margin ofthe panel a pocket 13. In the upper zone of the seat back the pockets 13house wires 14 which are engaged by hooks 8. The dimensions of the paneland hooks are chosen such that the upper panel portion is, in theillustrated installed condition, under the correct level of tension toprovide the desired support in the upper back region.

In the lower region of the panel the pockets 13 house the central region15 of strip spring steel springs 16. At the upper and lower ends of eachcentral region 15 each spring 16 emerges from its respective pocket 13and curves rearwardly of the seat back, as most clearly illustrated inFIG. 2. Close to the ends of each central region 15 is a respective hook8 engages the spring 16 to locate the lower panel portion in the frame 6and to apply the required cross-tension to the panel. The rearmost endof the upper curved region 17 of each spring is connected to a firstcross member 18 which spans the width of the panel. As will be wellunderstood from FIG. 2, the cross member 18 is located substantially tothe rear of the panel 9 and will not be "felt" by the user of the seat.A second cross member 19 interconnects the rearmost extremity of eachlower curved region 20 of the spring 16. Again, the cross member 19 islocated well to the rear of the plane of the panel.

The core 21 of a Bowden cable 22 is secured to the lower cross member 19and the sheath 23 of the Bowden cable is secured to the upper crossmember 18. Means (30) are provided for drawing the core 21 into thesheath 23, thereby reducing the spacing of the cross members 18, 19.This adjusting means may conveniently take the form of a manuallyrotatable knob connected to a suitable screw-threaded arrangement fordrawing the core 21 relative to the sheath 23. This manual adjustmentcan conveniently be provided on the side of the seat back. In thealternative, appropriate powered adjustment means may be provided.

The springs 16 are so shaped that the inherent resilience to the springmaterial will tend to straighten the central region 15 of each spring.In the relaxed condition of the springs the central regions 15 may beflat or slightly convex. In the installed condition the maximum possiblespacing of the cross members 18,19 is selected (by appropriate choice ofmeans limiting the movement of the Bowden cable 22) to produce thedesired "minimum" lumbar support for the seat. This desired minimumcondition may be a condition in which the central regions 15 aresubstantially straight, or may be a condition in which some convex curveto the central regions exists.

If increased lumbar support is required, the adjusting means isappropriately adjusted to draw the cross members 18,19 towards eachother. This action will cause the central regions 15 of the springs tobow forward and carry forward with them the panel material therebetween.This will increase the "firmness" of the lumbar region of the seat asrequired. If, after such adjustment, less lumbar support is subsequentlyrequired the adjusting means is simply operated to allow the crossmembers 18 and 19 to move apart under the inherent resilient effects ofthe springs.

It will be noted that a single panel 9 is utilized within the preferredembodiment of seat. With this arrangement, there is an automatic andsmooth transition from the lumbar region to the upper back regionregardless of the state of adjustment of the lumbar region. However, theinvention is not limited to this configuration and it may, under somecircumstances, be desirable to limit the extent of the lumbar regionpanel to the lumbar region itself.

Whilst in the preferred embodiment of the invention a single adjustableregion is provided in the seat, back it will be appreciated that morethan one adjustable region may be provided if desired.

Whilst the invention has been described with particular reference to apanel of material in accordance with our patent GB-A-1500725, it will beappreciated that other materials may be used to form the panel.

We claim:
 1. A seat back for use in a seat for adjustably supporting aback of an occupant, said seat back comprising: a rigid frame havingopposite sides between which is supported a flexible panel, marginalregions of the panel adjacent the opposite sides of the frame beingprovided with pockets in which are located central regions of respectivewire or strip springs, end regions of each spring extending outwardlyfrom its respective pocket and rearwardly in a curved manner; an uppercross member located rearwardly of the panel and interconnecting uppercurved regions of each spring; a lower cross member located rearwardlyof the panel and interconnecting lower curved regions of each spring;and means for forcing the upper and lower cross members towards eachother whereby the central regions of the springs are urged to bowforwardly and thereby increase the force which the panel located betweenthe central regions of the springs applies to a back of an occupant. 2.A seat back according to claim 1, wherein the panel comprises acomposite having at least one area of flexible fabric and at least onearea of elastomeric material, the respective areas being secured to eachother to permit resilient deformation of the panel.
 3. A seat backaccording to claim 2, wherein the panel comprises a central zone offabric, marginal zones of fabric, and at least two intermediate zones ofelastomeric material, each intermediate zone being secured to a marginalzone and the central zone.
 4. A seat back according to claim 2, whereinthe fabric is a woven material and is substantially inextensible and theelastomeric material is a rubber material which is secured to the fabricmaterial by vulcanising.
 5. A seat back according to claim 1, whereinthe panel extends upwardly within the seat back beyond the springs andis secured in an area above the springs to the rigid frame to providesupport for an upper back of an occupant, the panel extendingsubstantially a full height of the seat back.
 6. A seat back accordingto claim 1, wherein the means for moving the upper and lower crossmembers comprises a Bowden cable, a sheath of which is connected to onecross member and a core which is connected to the other cross member,and means secured to the frame for drawing the core through the sheathin order to move the cross members together.
 7. A seat back according toclaim 6, wherein the means for drawing the core of the Bowden cablethrough the sheath comprises a manually rotatable adjuster secured tothe frame.
 8. A seat back according to claim 6, wherein the means fordrawing the core of the Bowden cable through the outer sheath comprisespower driven means.
 9. A vehicle seat containing a seat back foradjustably supporting a back of an occupant, the seat back comprising arigid frame having opposite sides between which is supported a flexiblepanel, marginal regions of the panel adjacent the opposite sides of theframe being provided with pockets in which are located central regionsof respective wire or strip springs, end regions of each springextending outwardly from its respective pocket and rearwardly in acurved manner; an upper cross member located rearwardly of the panel andinterconnecting upper curved regions of each spring; a lower crossmember located rearwardly of the panel and interconnecting lower curvedregions of each spring; and means for forcing the upper and lower crossmembers towards each other whereby the central regions of the springsare urged to bow forwardly and thereby increase the force which thepanel located between the central regions of the springs applies to aback of an occupant.